Hello out there in the horse world. We are off to a busy start with many new podiatry cases, vaccinations, floats and yearly wellness exams.
I wanted to post a couple of recent cases that drive home two very important points regarding therapeutic shoeing. Both cases are in rocker shoes. One because of crushed heels and poor foot mass and the second due to a low grade navicular bone lesion. Both cases where started in rocker shoes and have been sound. However after another farriers reset without radiographic guidance as per request of the Owner to help reduce cost both horses went lame. I ruled out any likelihood of close nails and horses are exhibiting only low grade lameness.
After radiographs where performed and measurements taken the shoe and trim were slightly modified. Below are the differences in pre and post shoe measurements that seemed significant to me and could likely be the reason that both cases where not as sound as previously.
Take some time and compare and contrast each radiograph for each case.
Note the major differences in digital alignment, palmar angle, toe lever, tendon surface angle and suspensory ligament of navicular bone distance. The changes noted radiographically help explain why this horse would be lame. The mechanics governed by the trim, shape and placement of the rocker alter loads inside the foot. With the PA much lower a higher degree of tension can be expected within the deep digital flexor unit and more hyperextension applied to the coffin and pastern joint. A recent paper suggest that for every degree change in PA, pressure on the navicular bone changes 4%. We changed load on the navicular apparatus by around 24 %. Note the distance measured from the navicular bone to the origin of the suspensory ligament of the navicular bone. This changed 6mm and may also be another reason for increased comfort with higher mechanics. The last important aspect is the toe lever, measured from COA to where the shoe would leave the ground. This is the affective lever arm that gives the ground advantage to apply force to the flexor tendon apparatus. This number was greatly changed and subsequent reduction in force applied to DDFT is achieved.
This horse has mild navicular bone changes and has responded very nicely to the rocker shoe approach. The increased PA and reduced digital break over has this horse back in the show ring. This one has baffled me as after the farrier reset horse was just slightly off in soft footing and traveled almost normal on hard surface. On initial exam the PA and shoe placement appeared to be in good shape. However when in soft footing the horse would tend towards a rocking back approach, which I assumed to increase pressure on DDFT and navicular apparatus.
I wanted to post a couple of recent cases that drive home two very important points regarding therapeutic shoeing. Both cases are in rocker shoes. One because of crushed heels and poor foot mass and the second due to a low grade navicular bone lesion. Both cases where started in rocker shoes and have been sound. However after another farriers reset without radiographic guidance as per request of the Owner to help reduce cost both horses went lame. I ruled out any likelihood of close nails and horses are exhibiting only low grade lameness.
After radiographs where performed and measurements taken the shoe and trim were slightly modified. Below are the differences in pre and post shoe measurements that seemed significant to me and could likely be the reason that both cases where not as sound as previously.
Take some time and compare and contrast each radiograph for each case.
 |
| Farriers reset |
 |
| Post radiograph trim and shoe |
Note the major differences in digital alignment, palmar angle, toe lever, tendon surface angle and suspensory ligament of navicular bone distance. The changes noted radiographically help explain why this horse would be lame. The mechanics governed by the trim, shape and placement of the rocker alter loads inside the foot. With the PA much lower a higher degree of tension can be expected within the deep digital flexor unit and more hyperextension applied to the coffin and pastern joint. A recent paper suggest that for every degree change in PA, pressure on the navicular bone changes 4%. We changed load on the navicular apparatus by around 24 %. Note the distance measured from the navicular bone to the origin of the suspensory ligament of the navicular bone. This changed 6mm and may also be another reason for increased comfort with higher mechanics. The last important aspect is the toe lever, measured from COA to where the shoe would leave the ground. This is the affective lever arm that gives the ground advantage to apply force to the flexor tendon apparatus. This number was greatly changed and subsequent reduction in force applied to DDFT is achieved.
 |
| Farriers reset |
 |
| Post radiograph re trim and shoe |
The measurable differences are a shortened toe lever and a much lower PA, however the Suspensory ligament distance and the TSA remained very similar despite the lower PA. This is very confusing and I will continue to try to wrap my head around this one. I think the key here was reshaping the rocker to place directly under center of articulation versus slightly behind and modification of the trim in the same manner. I feel with the belly/rocker to far back this forced a higher than needed PA and created a scenerio that allowed for rapid sinking of the heel in soft footing. Jogged sound in hard and soft footing after changes where made.
Take home message:
1) Not all rocker shoes are the same.
2) Radiographs are a valuable tool in many difficult cases.
I feel that if radiographs where available, for the farriers that reset these shoes, this could have been avoided as there are obvious mechanical differences noted in the radiographs. Many times have I pulled a shoe and modified it after seeing the radiograph and I am thankful for that advantage.
Do not blame the anything but the mechanics! Do you really know what they are?
Note to Owners: Yes radiographs can be the difference between your horse being sound or lame.
Note to farriers and veterinarians: Do not blame the rocker shoe, heartbar, egg bar, or whatever device applied without critical evaluation of the mechanics that the foot is subjected to. If something did not work try to figure out why. Through serial radiographic evaluation of every foot problem one can develop an enormous amount of information and detail that can allow such great success.
All the best,
Sammy
Nice work. I have experimented some with this sort of shoeing both with and without rads, and I have wavered back and forth on the merits. I'm open enough to it that I've gone ahead and signed up for Redden's July course, but I continue to have a degree of skepticism. What is the longevity of the corrections made considering hoof growth, could you also post for comparative purposes the rads at the end of the shoeing cycle?
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